Polymer nanocomposites are an exciting class of hybrid materials that contain typically inorganic nanoparticles embedded in a polymer matrix, and this class of materials has attracted a lot of interest due to their promise in a number of technologies. As one example, in some membrane applications polymer nanocomposites have been shown to be capable of breaking the typical tradeoff between selectivity and permeability that is observed. However, despite their promise, there are numerous fundamental challenges that remain in the design of polymer nanocomposites. The thermodynamics of even simple polymer nanocomposites remain poorly understood, and direct mappings between theoretical and experimental phase diagrams are rare in the field. Furthermore, strategies for reaching high nanoparticle loadings are few. In this talk, I will describe recent efforts to address both the need to predict the thermodynamics of polymer nanocomposites and the properties of nanoparticles at high loadings. Our group has both developed a novel suite of field-theoretic simulations techniques to study inhomogeneous polymer/nanoparticle composites, which enable the prediction of phase diagrams for this class of hybrid materials, and we have recently extended our methods to capture beyond-equilibrium phenomena to describe systems where processing plays a key role in the resulting structure. Separately, we have characterized the properties of a novel class of nanocomposites where the nanoparticles are loaded at high concentrations, up to random close packing. In these materials, the entropy of the polymer in this highly confined geometry plays a key role in both the formation and the properties of the composite.
Robert Riggleman received a B.S. in Chemical Engineering from the University of South Carolina, Columbia, and a Ph.D. in Chemical Engineering from the University of Wisconsin, Madison, where he was co-advised by Profs. Juan de Pablo and Paul Nealey. After his postdoctoral studies at the University of California, Santa Barbara, with Prof. Glenn Fredrickson, he joined the faculty in the School of Engineering and Applied Science at the University of Pennsylvania in 2010. He has been recently promoted to Associate Professor with tenure, effective July 2017. His research uses molecular dynamics, Monte Carlo, and field-theoretic simulations to study fundamental problems related to the dynamics and thermodynamics of soft materials.
Seminar sponsored by the Department of Chemical and Biomolecular Engineering